Twinsen under the rain, in Desert Island, without his tunic.
There is a glitch in LBA2, that lets Twinsen travel from Citadel Island to Desert Island using the ferry, without stopping the storm. He can even go without his tunic.
To do this, Twinsen must buy the Ferry ticket in the harbor, and use it in the dock, in the spot where the ferry should be. If he does this, he will disappear, and the ferry ticket will appear in the top left of the screen as having been used. Nothing will happen until the player presses "Esc", and Twinsen will be transported to Desert Island.
There's no difference in Desert Island with this glitch, except that it's raining, and that Twinsen can be there without the tunic. But he can do anything that could do normally. The Esmers are there (because Twinsen isn't supposed to be there until they arrive at Twinsun).
The only thing that stops Twinsen from continuing the story, is that when he heals the injured Dino-Fly, and tries to talk to him so he can go to the Island of the Dome of the Slate, the Dino-Fly acts as he would be still injured, so Twinsen can't reach the island, and therefore, can't become a wizard. The only way to continue the story is using the Jump Save Bug.